Answer: Hemlock woolly adelgids are small, aphid-like, sap-sucking insects that concentrate their feeding activities on the youngest branches of a hemlock, where the needles attach to the twig. The feeding kills the needles and interferes with the trees ability to produce new ones. It's easy to recognize an infestation -- the insects are named for the white, fuzzy eggsac they lay along young twigs, at the base of almost every needle. Infested limbs may die in one growing season, and entire trees often succumb within 1 to 4 years.
If you are trying to control adelgids on one or a few small trees, you can try a horticultural oil to smother the eggs, crawlers and flying adults when they are vulnerable. Insecticidal soap also gives good control. If you are dealing with a large stand of trees, or very large trees, contact a county forester or local arborist.
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